JIS H5120 CAC406, a bronze alloy which has been conventionally used for parts in materials and equipment for water works and in feed water supply system, contains from 4.0 to 6.0% by weight of lead, and the lead leaching therefrom into the tap water has been frequently observed. Therefore, in order to reduce the amount of toxic lead leaching, the production of a copper alloy containing a reduced amount of lead, or a lead-free copper alloy which contains no lead has been investigated.
However, when a copper alloy is produced without lead, or with a reduced amount of lead, the castability, machinability, and/or the water pressure resistance of the resulting copper alloy are reduced, thereby causing the leaking of water when the alloy is used in a valve, for example. Therefore, an alloy has been investigated in which not only the content of lead is reduced, but also the deterioration of functional properties, such as a decrease in the water pressure resistance, is prevented as much as possible as compared to the alloy containing lead.
For example, JP 2889829 B describes a bronze alloy which contains from 0.5% to 6% by weight of Bi and from 0.05% to 3% by weight of Sb, to compensate for the reduced lead content. Particularly, Example 7 therein describes that a bronze alloy which contains 1.5% by weight of Sn; 17.5% by weight of Zn, 0.7% by weight of Bi, 0.06% by weight of Sb, 0.003% by weight of P, and 0.8% by weight of Ni, and in which the content of Pb is reduced to 0.1% by weight, provided suitable results.
Further, JP 4866717 B describes a copper alloy for use in a member for water works which exhibits suitable properties despite a reduced lead content, as a result of containing from 2.0% to 3.0% by weight of Ni, and from 0.5% to 1.1% by weight or less of Bi.
In addition, JP 4294793 B describes a bronze alloy which contains from 1.5% to 2.5% by mass of Bi and from 0.1% to 0.5% by mass of Ni.
However, recent researches have reported the results which suggest an undeniable possibility that the Ni, which is contained in the alloy disclosed in Example 7 of JP 2889829 B and the alloy disclosed in JP 4866717 B, could cause an allergy. Therefore, from now on, it is considered that reducing the Ni content as much as possible is preferred, even in the material for use in a member for water works. On the other hand, since the bronze alloy disclosed in JP 4294793 B contains too high an amount of Bi despite a low Ni content, it has been found that, when subjected to sand casting, the resulting casting is prone to shrinkage cavities and tends to have reduced mechanical properties.